/*-------------------------------------------------------------------------
 *
 * nodeGroup.c--
 *    Routines to handle group nodes (used for queries with GROUP BY clause).
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * DESCRIPTION
 *    The Group node is designed for handling queries with a GROUP BY clause.
 *    It's outer plan must be a sort node. It assumes that the tuples it gets
 *    back from the outer plan is sorted in the order specified by the group
 *    columns. (ie. tuples from the same group are consecutive)
 *
 * IDENTIFICATION
 *    $Header: /usr/local/cvsroot/postgres95/src/backend/executor/nodeGroup.c,v 1.5 1997/01/10 20:17:35 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <string.h>

#include "postgres.h"
#include "fmgr.h"

#include "access/heapam.h"
#include "catalog/catalog.h"
#include "access/printtup.h"
#include "executor/executor.h"
#include "executor/nodeGroup.h"

static TupleTableSlot *ExecGroupEveryTuple(Group *node);
static TupleTableSlot *ExecGroupOneTuple(Group *node);
static bool sameGroup(TupleTableSlot *oldslot, TupleTableSlot *newslot,
		      int numCols, AttrNumber *grpColIdx, TupleDesc tupdesc);

/* ---------------------------------------
 *   ExecGroup -
 *
 *	There are two modes in which tuples are returned by ExecGroup. If
 *	tuplePerGroup is TRUE, every tuple from the same group will be
 *	returned, followed by a NULL at the end of each group. This is
 *	useful for Agg node which needs to aggregate over tuples of the same
 *	group. (eg. SELECT salary, count{*} FROM emp GROUP BY salary)
 *
 *	If tuplePerGroup is FALSE, only one tuple per group is returned. The
 *	tuple returned contains only the group columns. NULL is returned only
 *	at the end when no more groups is present. This is useful when
 *	the query does not involve aggregates. (eg. SELECT salary FROM emp
 *	GROUP BY salary)
 * ------------------------------------------
 */
TupleTableSlot *
ExecGroup(Group *node)
{
    if (node->tuplePerGroup)
	return ExecGroupEveryTuple(node);
    else
	return ExecGroupOneTuple(node);
}

/*
 * ExecGroupEveryTuple -
 *   return every tuple with a NULL between each group
 */
static TupleTableSlot *
ExecGroupEveryTuple(Group *node)
{
    GroupState		*grpstate;
    EState		*estate;
    ExprContext		*econtext;

    HeapTuple 		outerTuple = NULL;
    TupleTableSlot 	*outerslot, *lastslot;
    ProjectionInfo	*projInfo;
    TupleTableSlot	*resultSlot;

    bool isDone;

    /* ---------------------
     *  get state info from node
     * ---------------------
     */
    grpstate = node->grpstate;
    if (grpstate->grp_done)
	return NULL;

    estate = node->plan.state;

    econtext = grpstate->csstate.cstate.cs_ExprContext;

    if (grpstate->grp_useLastTuple) {
	/*
	 * we haven't returned last tuple yet because it is not of the
	 * same group
	 */
	grpstate->grp_useLastTuple = FALSE;

	ExecStoreTuple(grpstate->grp_lastSlot->val,
		       grpstate->csstate.css_ScanTupleSlot,
		       grpstate->grp_lastSlot->ttc_buffer,
		       false);
    } else {
	outerslot = ExecProcNode(outerPlan(node), (Plan*)node);
	if (outerslot)
	    outerTuple = outerslot->val;
	if (!HeapTupleIsValid(outerTuple)) {
	    grpstate->grp_done = TRUE;
	    return NULL;
	}

	/* ----------------
	 *  Compare with last tuple and see if this tuple is of
	 *  the same group.
	 * ----------------
	 */
	lastslot = grpstate->csstate.css_ScanTupleSlot;

	if (lastslot->val != NULL &&
	    (!sameGroup(lastslot, outerslot,
			node->numCols, node->grpColIdx,
			ExecGetScanType(&grpstate->csstate)))) {
/*			ExecGetResultType(&grpstate->csstate.cstate)))) {*/

	    grpstate->grp_useLastTuple = TRUE;

	    /* save it for next time */
	    grpstate->grp_lastSlot = outerslot;

	    /*
	     * signifies the end of the group 
	     */
	    return NULL;
	}
	
	ExecStoreTuple(outerTuple,
		       grpstate->csstate.css_ScanTupleSlot,
		       outerslot->ttc_buffer,
		       false);
    }

    /* ----------------
     *	form a projection tuple, store it in the result tuple
     *  slot and return it.
     * ----------------
     */
    projInfo = grpstate->csstate.cstate.cs_ProjInfo;

    econtext->ecxt_scantuple = grpstate->csstate.css_ScanTupleSlot;
    resultSlot = ExecProject(projInfo, &isDone);
    
    return resultSlot;
}

/*
 * ExecGroupOneTuple -
 *    returns one tuple per group, a NULL at the end when there are no more
 *    tuples.
 */
static TupleTableSlot *
ExecGroupOneTuple(Group *node)
{
    GroupState		*grpstate;
    EState		*estate;
    ExprContext		*econtext;

    HeapTuple 		outerTuple = NULL;
    TupleTableSlot 	*outerslot, *lastslot;
    ProjectionInfo	*projInfo;
    TupleTableSlot	*resultSlot;

    bool isDone;

    /* ---------------------
     *  get state info from node
     * ---------------------
     */
    grpstate = node->grpstate;
    if (grpstate->grp_done)
	return NULL;

    estate = node->plan.state;

    econtext = node->grpstate->csstate.cstate.cs_ExprContext;

    if (grpstate->grp_useLastTuple) {
	grpstate->grp_useLastTuple = FALSE;
	ExecStoreTuple(grpstate->grp_lastSlot->val,
		       grpstate->csstate.css_ScanTupleSlot,
		       grpstate->grp_lastSlot->ttc_buffer,
		       false);
    } else {
	outerslot = ExecProcNode(outerPlan(node), (Plan*)node);
	if (outerslot) outerTuple = outerslot->val;
	if (!HeapTupleIsValid(outerTuple)) {
	    grpstate->grp_done = TRUE;
	    return NULL;
	}
	ExecStoreTuple(outerTuple,
		       grpstate->csstate.css_ScanTupleSlot,
		       outerslot->ttc_buffer,
		       false);
    }
    lastslot = grpstate->csstate.css_ScanTupleSlot;

    /*
     * find all tuples that belong to a group
     */
    for(;;) {
	outerslot = ExecProcNode(outerPlan(node), (Plan*)node);
	outerTuple = (outerslot) ? outerslot->val : NULL;
	if (!HeapTupleIsValid(outerTuple)) {
	    /*
	     * we have at least one tuple (lastslot) if we reach here
	     */
	    grpstate->grp_done = TRUE;

	    /* return lastslot */
	    break;
	}

        /* ----------------
	 *  Compare with last tuple and see if this tuple is of
	 *  the same group.
	 * ----------------
	 */
	if ((!sameGroup(lastslot, outerslot,
			node->numCols, node->grpColIdx,
			ExecGetScanType(&grpstate->csstate)))) {
/*			ExecGetResultType(&grpstate->csstate.cstate)))) {*/

	    grpstate->grp_useLastTuple = TRUE;

	    /* save it for next time */
	    grpstate->grp_lastSlot = outerslot;

	    /* return lastslot */
	    break; 
	}
	
	ExecStoreTuple(outerTuple,
		       grpstate->csstate.css_ScanTupleSlot,
		       outerslot->ttc_buffer,
		       false);

	lastslot = grpstate->csstate.css_ScanTupleSlot;
    }

    ExecStoreTuple(lastslot->val,
		   grpstate->csstate.css_ScanTupleSlot,
		   lastslot->ttc_buffer,
		   false);

    /* ----------------
     *	form a projection tuple, store it in the result tuple
     *  slot and return it.
     * ----------------
     */
    projInfo = grpstate->csstate.cstate.cs_ProjInfo;

    econtext->ecxt_scantuple = lastslot;
    resultSlot = ExecProject(projInfo, &isDone);
    
    return resultSlot;
}

/* -----------------
 * ExecInitGroup 
 *
 *  Creates the run-time information for the group node produced by the
 *  planner and initializes its outer subtree
 * -----------------
 */
bool
ExecInitGroup(Group *node, EState *estate, Plan *parent)
{
    GroupState		*grpstate;
    Plan		*outerPlan;
    
    /* 
     * assign the node's execution state
     */
    node->plan.state = estate;
    
    /*
     * create state structure
     */
    grpstate = makeNode(GroupState);
    node->grpstate = grpstate;
    grpstate->grp_useLastTuple = FALSE;
    grpstate->grp_done = FALSE;

    /*
     * assign node's base id and create expression context
     */
    ExecAssignNodeBaseInfo(estate, &grpstate->csstate.cstate,
			   (Plan*) parent);
    ExecAssignExprContext(estate, &grpstate->csstate.cstate);
    
#define GROUP_NSLOTS 2
    /*
     * tuple table initialization
     */
    ExecInitScanTupleSlot(estate, &grpstate->csstate);
    ExecInitResultTupleSlot(estate, &grpstate->csstate.cstate);

    /*
     * initializes child nodes
     */
    outerPlan = outerPlan(node);
    ExecInitNode(outerPlan, estate, (Plan *)node);
    
    /* ----------------
     * 	initialize tuple type.
     * ----------------
     */
    ExecAssignScanTypeFromOuterPlan((Plan *) node, &grpstate->csstate); 

    /*
     * Initialize tuple type for both result and scan.
     * This node does no projection
     */
    ExecAssignResultTypeFromTL((Plan*) node, &grpstate->csstate.cstate);
    ExecAssignProjectionInfo((Plan*)node, &grpstate->csstate.cstate);

    return TRUE;
}

int
ExecCountSlotsGroup(Group *node)
{
    return ExecCountSlotsNode(outerPlan(node)) + GROUP_NSLOTS;
}

/* ------------------------
 *	ExecEndGroup(node)
 *
 * -----------------------
 */
void
ExecEndGroup(Group *node)
{
    GroupState	*grpstate;
    Plan	*outerPlan;

    grpstate = node->grpstate;

    ExecFreeProjectionInfo(&grpstate->csstate.cstate);

    outerPlan = outerPlan(node);
    ExecEndNode(outerPlan, (Plan*)node);
    
    /* clean up tuple table */
    ExecClearTuple(grpstate->csstate.css_ScanTupleSlot);
}

/*****************************************************************************
 *
 *****************************************************************************/

/*
 * code swiped from nodeUnique.c
 */
static bool
sameGroup(TupleTableSlot *oldslot,
	  TupleTableSlot *newslot,
	  int		 numCols,
	  AttrNumber	 *grpColIdx,
	  TupleDesc	 tupdesc)
{
    bool isNull1,isNull2;
    char *attr1, *attr2;
    char *val1, *val2;
    int i;
    AttrNumber att;
    Oid typoutput;

    for(i = 0; i < numCols; i++) {
	att = grpColIdx[i];
	typoutput = typtoout((Oid)tupdesc->attrs[att-1]->atttypid);    

	attr1 = heap_getattr(oldslot->val,
			     InvalidBuffer,
			     att,
			     tupdesc,
			     &isNull1);

	attr2 = heap_getattr(newslot->val,
			     InvalidBuffer, 
			     att,
			     tupdesc,
			     &isNull2);
			     
	if (isNull1 == isNull2) {
	    if (isNull1) /* both are null, they are equal */
	      continue;

	    val1 = fmgr(typoutput, attr1,
			gettypelem(tupdesc->attrs[att-1]->atttypid));
	    val2 = fmgr(typoutput, attr2,
			gettypelem(tupdesc->attrs[att-1]->atttypid));

	    /* now, val1 and val2 are ascii representations so we can
	       use strcmp for comparison */
	    if (strcmp(val1,val2) != 0)
		return FALSE;
	} else {
	    /* one is null and the other isn't, they aren't equal */
	    return FALSE;
	}
    }

    return TRUE;
}
